Windshear may be defined as a condition that exists where the velocity and/or direction of the wind is significantly changing with relatively small changes in altitude. It also refers to serious microbursts, which are violent downburst of air which are particularly hazardous when an aircraft is descending through an air mass while making an approach to an airport.
The problems associated with microbursts which are referred to herein as serious windshear have been recognized since as early as 1977. Prior to that time microbursts were responsible for a number of accidents involving commercial airlines. Efforts were made to overcome the problem. However, the first successful approach to overcome such problems is disclosed in my U.S. Pat. No. 4,012,713 entitled, “System for Providing An Indication of Windshear.” As described therein, a system for generating a windshear signal representing the windshear condition encountered by an aircraft includes means for generating a signal representing the rate of change of the instantaneous airspeed of the aircraft. The system also includes means for generating a signal representing the horizontal inertial acceleration of the aircraft and means for subtracting the horizontal inertial acceleration signal from the rate of change of instantaneous airspeed signal to provide a windshear or microbursts signal. In addition, the system may include means for processing the windshear signal to provide an indication representing the magnitude thereof. In a commercial embodiment of this invention, the system includes an audio warning to a pilot that the aircraft is approaching a dangerous windshear condition and that immediate corrective action should be taken.
There have been a number of other patents on windshear detection as for example, a U.S. patent of Glover, U.S. Pat. No. 6,188,330. As disclosed by Glover, a windshear detection system uses parameters provided by standard on-board air data management installed detection systems and in which no accelerometers are required. The system uses the following inputs; aircraft true airspeed, aircraft inertial ground speed, aircraft vertical speed, aircraft angle of attack, aircraft pitch angle and aircraft whole attitude (θ) from a vertical gyro.
An additional U.S. patent of Lebrun, U.S. Pat. No. 4,281,383 discloses a system for detecting a wind radiant that utilizes the aerodynamic incline or flight path angle, the total flight path angle and the difference between the selected speed during the approach and the airspeed. The system also incorporates two accelerometers whose sensing axes are oriented parallel to the rolling axis and parallel to the pitch angle.
It is now believed that there will be a commercial market for a windshear detection and warning system in accordance with the present invention. It is believed that there will be a commercial market for such systems because they eliminate the need for determining inertial ground speed, aircraft vertical speed, aircraft pitch attitude and use of a vertical gyro and/or an inertial reference system.
Additionally, the windshear detection and warning system in accordance with the present invention are based solely on the relationship between changes in an aircraft's airspeed and its angle of attack. Such systems require only an angle of attack indicator, an airspeed indicator and a processor for comparing the relationship of the two values. It also requires an input of a threshold level to eliminate false warnings as well as a preselected time to eliminate a warning due to wind gusts. Accordingly, it is believed that the systems in accordance with the present invention are particularly suitable for general aviation and other aircraft that are not equipped with sophisticated aerodynamics. Further, such systems can be sold at a relatively low cost, facilitate installation and repair, are of relatively lightweight and durable. Therefore, such systems should appeal to the owners and operators of relatively small aircraft.